1. Field of the Invention
The present invention relates to a pointer that is employed in an instrument which is mounted on a vehicle, an airplane, a ship, etc.
2. Description of the Related Art
A self-luminous pointer is widely used as a pointer employed in an instrument. A conventional self-luminous pointer is disclosed in Japanese Unexamined Patent Publication No. H11-194040.
As shown in FIG. 1, a pointer 100 comprises an attached portion 101 and a tapered main body 102. The attached portion 101 is attached to a rotary shaft of an instrument (not shown). The main body 102 is fixed to the attached portion 101 at a basic portion thereof and extends toward a free portion thereof. The attached portion 101 and the main body 102 are made of light transmission members.
As shown in FIG. 2, an entrance face 103 is formed at a bottom of the basic portion of the main body 102. Light emitted from a light source (not shown) enters the main body 102 through the entrance face 103. A reflective surface 104 is formed at an inclined side of the basic portion of the main body 102. The reflective surface 104 is inclined at a θ degree angle relative to a traveling direction of light entering the main body 102.
The reflective surface 104 is curved like a collective convex lens in a transverse direction N. The reflective surface 104 extends straight in an inclined direction M. The transverse direction N is perpendicular to the inclined direction M. The collective convex lens has the smallest curvature at an upper end of the reflective surface 104 (see FIG. 3) and the largest curvature at a lower end of the reflective surface 104 (see FIG. 4). A curvature of the collective convex lens successively changes between the upper and lower ends.
A foil-stamping layer 105 is formed on a bottom surface of the main body 102. The foil-stamping layer 105 is colored and serves as a light diffusion surface.
In the above structure, light L enters the main body 102 through the entrance face 103 and then is reflected by the reflective surface 104. Light L1 reflected on an upper end region of the reflective surface 104 goes straight ahead in main body 102 and then is diffusely reflected by the foil-stamping layer 105. Also, light L2 reflected on a lower end region of the reflective surface 104 goes straight ahead in main body 102 and then is diffusely reflected by the foil-stamping layer 105. Therefore, the light L1 and the light L2 evenly lighten the main body 102. As a result, an operator can recognize the pointer 100 clearly.
However, the pointer 100 is very sensitive to the oblique angle θ relative to the traveling direction of light entering the main body 102. More specifically, if the oblique angle θ is large, light reflected by the reflective surface 104 collects in the vicinity of the basic portion of the main body 102. In contrast, if the oblique angle θ is small, light reflected by the reflective surface 104 collects in the vicinity of the free portion of the main body 102. Therefore, it is hard to adjust the oblique angle θ such that the light reflected by the reflective surface 104 evenly lighten the main body 102. This leads to a poor handling.